Ventilation device

Abstract: A ventilation device comprising a cross-flow type heat exchanger mounted at a crossing point of an exhausted ambient air path and an intake air path. The device further comprises an intake resp. an exhaust air chamber situated upstream resp. downstream of the heat exchanger, said intake resp. exhaust air chamber having an output resp. an input plane extending substantially parallel to an input resp. an output plane of said heat exchanger.

Description: The present invention relates to a ventilation device, in particular a kitchen hood, comprising: a suction opening for the input of ambient air to be removed out of a room and connected via a first air path to an exhaust duct for exhausting said removed ambient air; an intake air duct connected via a second air path to an air discharge opening provided for the output of an intake air flow; a cross-flow type heat exchanger mounted at a crossing point of said first and second air path and provided for extracting heat out of said ambient air and transferring it to said intake air; an intake air chamber crossed by said second air path and situated upstream of said heat exchanger and having an output plane extending substantially parallel to an input plane of said heat exchanger. an exhaust air chamber crossed by said first air path and situated downstream of said heat exchanger and having an input plane extending substantially parallel to an output plane of said heat exchanger. Such a ventilation device is known from EP-A-0.284.142. In the known ventilation device the removed ambient air is guided towards the input of the heat exchanger, where the heat extracted form that ambient air is supplied to fresh air in order to heat up the latter. The thus warmed up fresh air is then supplied to the room. In order to increase the heat exchange flue gases, produced by a combustion boiler, are also directed towards the heat exchanger. In such a manner heat is extracted from the flue gases by the heat exchanger and supplied to the fresh air. A drawback of the known ventilation device is that flue gases and air exhausted from a room are travelling in parallel through the heat exchanger and mix up at the output of the heat exchanger. Special precautions such as flaps have to be provided in order to prevent a flow back of the flue gases in the room. The latter renders such a device expensive and there will still be a risk that flue gases reaches the room. The object of the present invention is to improve the heat exchange efficiency of the ventilation device without the supply of an external heat source such as a boiler device. A ventilation device according to the present invention is therefor characterised in that said intake air chamber comprises a separation wall made of heat conductive material and separating said intake air chamber from an exhaust air collector situated downstream of said suction opening in front of said heat exchanger. The separation wall not only enables to separate the ambient air to be exhausted from the introduced fresh air, but also due, to the use of heat conductive material, to extract heat from the ambient air and supply it to the fresh air. An improved heat exchange is thus obtained as the separation wall, together with the heat exchanger, contribute to the heat exchange between ambient air and fresh air. A first preferred embodiment of a ventilation device according to the invention is characterised in that said separation wall being in line with the ambient air entrance of said heat exchanger. This enables to facilitate the construction of the ventilation device on one hand and to avoid turbulences which would perturb the flow of exhaust air into the heat exchanger. Preferably, the ventilation device comprises a grease filter situated between said suction opening and said heat exchanger, said grease filter being inclined over an angle situated between 5-75° with respect to the ambient air entrance plane of said heat exchanger. The heat exchanger can thus be removed through the opening provided for the grease filter. The invention will now be described in more details by referring to the annexed drawings showing an example of a ventilation device according to the invention. In the drawings : Figure 1 shows a schematic view of a ventilation device according to the invention. Figure 2 illustrates the air flow within the cross-flow type heat exchanger. Figure 3 shows a cross-sectional view through a ventilation device according to the invention. Figure 4 shows an alternative embodiment of a ventilation device according to the invention. In the drawings, a same reference number is assigned to a same or an analogous element. The ventilation device 1 illustrated in figure 1 comprises an intake air duct 2 and an exhaust duct 3. In figure 1, the intake and exhaust ducts are shown close to each other. They could however also be at a distance from each other since the exhaust resp. the intake duct can be applied at any place along the line AB resp. CD. The intake air duct 2 flows into an intake air chamber 4, while an exhaust air chamber 5 is connected with said exhaust duct 3. The intake air chamber is delimited by the frame of the ventilation device and the separation walls 15 and 16 (figure 3). The separation wall 15 resp. 16 forms the separation between the intake air chamber and an exhaust air collector 12 resp. the exhaust air chamber 5. A heat exchanger 6 is mounted between the exhaust air collector 12 and the exhaust chamber. The ambient air to be removed from the place where the ventilation device is placed enters the device via a suction opening 14 and is collected in the exhaust air collector 12. The collected ambient air then flows via the heat exchanger towards the exhausted chamber 5. The path along which the exhaust ambient air travels with the device is indicated by the arrow 10 and will be referred to as a first air path. The intake air, preferably fresh air supplied from outside the room where the device is mounted, travels along a second air path indicated by the arrow 11. That second air path extends through the intake air chamber 4, the heat exchanger 6 and a further chamber 8 situated downstream of the heat exchanger towards an air discharge opening 9. In the embodiment shown in figure 1, the air discharge opening is applied in a sidewall of the ventilation device, outside the plane wherein the suction opening 14 is situated, and is provided for the output of the intake air flow into the room where the device is placed. In the alternative embodiment shown in figure 4, the air discharge opening 9 is situated on top of the device. The air discharge opening 9 is connected with an air duct 18. The latter embodiment enables to bring the intake air to a place removed from the one where the ventilation device 1 is mounted. By crossing the heat exchanger, heat is extracted from the ambient air and transferred to the intake air in order to heat up the latter by means of heat recuperated from the removed ambient air. The heat exchanger 6 is of the cross-flow type, as is illustrated in figure 2, and is located at the crossing point of the first 10 and second 11 air path. Cross-flow type heat exchanger signifies that by crossing the heat exchanger, the ambient air and the intake air crosses each other without interfering physically with each other. Such a heat exchanger is known as such and is for example commercialized by Heatex AB. The heat exchanger extends over substantially the whole length of the ventilation device. The intake resp. output air chamber 4 resp. 5 has an output resp. input plane directly upstream resp. downstream the air entrance resp. output of the heat exchanger. The surface of that output resp. input plane extends substantially parallel to the intake air input resp. ambient air output of the heat exchanger. In such a manner, the intake resp. ambient air can directly stream into our out of the heat exchanger without being bent directly at the entrance or output of the heat exchanger. The latter substantially increases the throughput through the heat exchanger since large circulation facilities are thus provided. The dimension of the heat exchanger is preferably chosen in such a manner that the length 1 of the intake air input plane is longer than the distance d covered by the intake air flow while crossing the heat exchanger. The heat exchanger is therefore preferably dimensioned in such a manner that the ratio between the height h of the heat exchanger input surface for the intake air and the distance d covered by the intake air flow while crossing the heat exchanger is at least equal to one : h/d ≥ 1 Preferably, the heat exchanger is rectangularly shaped which enables an easy and compact construction while at the same time satisfying the latter dimension constraints. The particular dimensioning of the heat exchanger combined with the use of a cross-flow type heat exchanger enables to provide, as well for the intake air as for the ambient air, a heat exchanger entrance surface which extends over substantially the whole length of the ventilation device. There is thus no need to canalize neither the intake air nor the ambient air towards a restricted input area of the heat exchanger to avoid interference. Further turbulence in the air stream which would reduce the through-put of the air circulating through the heat exchanger are avoided in such a manner. The fact that the heat exchanger can, now be extended over the whole length of the device enables that for a given length of the device the heat exchanger is operative over the whole length thus enabling an increased efficiency with respect to a heat exchanger which extends only over a part of this given length due to construction constraints. The heat exchanger is formed either by a single module or by a series of modules placed subsequent to each other. The latter is a preferred embodiment for a ventilation device having a length of 80 cm or more. Each module preferably has a length of 40 cm. The use of subsequent modules enables to more easily remove the different modules, for example for cleaning purposes. The use of a cross-flow heat exchanger enables to substantially simplify the construction of the ventilation device, while at the same time improving its efficiency. The separation wall 15 separating the intake air chamber 15 from the exhaust air collector 12 is preferably made of heat conductive material. The ambient air collected in the exhaust air collector enters into contact with that separation wall 15 and thus heats the wall up. Since the separation wall is made of heat conductive material, the heat thus extracted from the ambient air present in the exhaust air collected is transferred to the intake air chamber where it can heat up the intake air before the latter enters into the heat exchanger. The separation wall 15 thus also contributes to the heat transfer and improves in such a manner the heat transfer efficiency of the whole device. The fact that the separation wall 15 can be mounted so close to the exhaust air collector is due to the fact that a cross-flow type heat exchanger is used enabling crossing of the first and second air path so close to the place where the ambient air enters the device. The heat exchanger 6 is mounted inclined over an angle α with respect to the plane wherein the suction opening 14 is located. The angle α is situated between 0 and 45°, preferably 30°. This enables to reduce the total height of the device and to increase the volume of the exhaust air collector 12. The latter improving the security of the device because it enables to provide a larger distance between a grease filter 7 situated at the entrance of the exhaust air collector and the ambient air entrance of the heat exchanger. In particular when the ventilation device is used as a kitchen hood, the greater the distance between the grease filter and the heat exchanger, the less the probability of grease particles to reach the heat exchanger. Another advantage of increasing the volume of the exhaust air collector 12 is that in such a manner space is provided for mounting a fire or heat detector even as fire extinguishing means within that collector 12. The exhaust air collector space being the one where the probability that a fire ignites being the largest, the presence of such a detector and fire extinguishing means in that collector space substantially improves the safety and reliability of the device. The grease filter 7 is also inclined, over an angle β with respect to the suction opening 14. The angle β is situated between 5-75°, preferably 35°. The angles α and β are preferably different from one another and chosen in such a manner that the heat exchanger can pass through the grease filter opening when the latter is removed from the device. This enables an easy removing of the heat exchanger with no need to remove other parts of the ventilation device than the grease filter. Depending on the overall dimension of the ventilation device, the angles α and β are chosen in such a manner as to enable a reduced overall length of the device while at the same time having a substantial volume for the exhaust air collector 12 and the intake air chamber 4. When the ventilation device has also to be used as a heating device for the ambient air, the latter is provided with heating means (not shown) situated in front of the air discharge opening 9.

Claims: A ventilation device, in particular a kitchen hood (1), comprising: a suction opening (14) for the input of ambient air to be removed out of a room and connected via a first air path (10) to an exhaust duct (3) for exhausting said removed ambient air; an intake air duct (2) connected via a second air path (11) to an air discharge opening (9) provided for the output of an intake air flow; a cross-flow type heat exchanger (6) mounted at a crossing point of said first and second air path (10,11) and provided for extracting heat out of said ambient air and transferring it to said intake air; an intake air chamber (4) crossed by said second air path (11) and situated upstream of said heat exchanger (6) and having an output plane extending substantially parallel to an input plane of said heat exchanger (6); an exhaust air chamber (5) crossed by said first air path (10) and situated downstream of said heat exchanger (6) and having an input plane extending substantially parallel to an output plane of said heat exchanger (6); characterised in that said intake air chamber (4) comprises a separation wall (15) made of heat conductive material and separating said intake air chamber (4) from an exhaust air collector (12) situated downstream of said suction opening (14) in front of said heat exchanger (6). A ventilation device as claimed in claim 1, characterised in that said separation wall (15) is in line with the ambient air entrance of said heat exchanger (6). A ventilation device as claimed in claim 1 or 2, characterised in that it comprises a grease filter (7) situated between said suction opening and said heat exchanger (6), said grease filter being inclined over an angle situated between 5-75° with respect to the ambient air entrance plane of said heat exchanger. A ventilation device as claimed in any one of the claims 1-3, characterised in that said intake air duct (2) and said exhaust air duct (3) extend in parallel to each other.

Inventors: MERTENS WIM, MERTENS, WIM
Applicants: KOBRA NAAMLOZE VENNOOTSCHAP DE, DE KOBRA, NAAMLOZE VENNOOTSCHAP
Application year: 1994
Main classification: F24C15
IPC codes: F24C15